Institute of Epidemiology and Medical Biometry, University of Ulm, Ulm, Germany.;
Kaiser-Friedrich-Ring 77, Wiesbaden, Germany;
Medical Science Department, Kyberg Vital GmbH, Oberhaching, Germany;
Amino; Acids; Immune; System; Vitamins; Common; Cold; Chronic; Infection; of; Ear; Nose; Pharyngeal; Area;